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"Blocklisted IP" - More Information

What is a Blocklisted IP?

The web site that you are attempting to access is being blocked by an “IP address Blocklist.”  IT@JH Enterprise Technology Services Network Security subscribes to 1 or more commercially available IP Blocklists. These lists are designed to provide a "near realtime" source of protection from malicious content or activity on or from the Internet. These IP blocklists are updated and refreshed throughout each day, 365 days per year.


A threat reduction tool known as an "IP Blocklist" is used by IT@JH Enterprise Technology Services Network Security to block "known bad" IP addresses.   These “blocklisted” IP addresses are associated with web sites or Internet mail systems that have been observed by worldwide network security sensors to contain, propagate, or spread one or more of the following:

What Can I Do?

You can contact the owner of the web resource that you are trying to reach to let them know that the IP address for their web presence is on 1 or more Internet IP address blocklists. They can work to clean their systems and get the system IP address off the blocklists.  Also, the owner of the web resource may be able to have the web resource moved to a different IP address.

Business Need for Blocklisted IP Web Resource (also known as "Allowlisting")

When there is a legitimate business need for the blocked or “blocklisted” web resource to be available on the JH Network, IT@JH Enterprise Technology Services Network Security Staff can be requested to perform a risk assessment on the blocklisted IP.  Johns Hopkins has the capability to allow access ("allowlist") blocklisted web sites in cases where there may be a critical dependency or business need.

Submit your IP allowlist request via email to Please specify the IP address or web address that you need to access, identify the business need, and include a daytime telephone number where you can be reached. The request will be evaluated based on recent activity and risk to the Hopkins network.